delta/go-git.git/src/runtime/vdso_linux.go, branch dev.boringcrypto.go1.12

all: use "reports whether" consistently instead of "returns whether"

2018-12-02T15:12:26+00:00

Follow-up for CL 147037 and after Brad noticed the "returns whether"
pattern during the review of CL 150621.

Go documentation style for boolean funcs is to say:

    // Foo reports whether ...
    func Foo() bool

(rather than "returns whether")

Created with:

    $ perl -i -npe 's/returns whether/reports whether/' $(git grep -l "returns whether" | grep -v vendor)

Change-Id: I15fe9ff99180ad97750cd05a10eceafdb12dc0b4
Reviewed-on: https://go-review.googlesource.com/c/150918
Run-TryBot: Tobias Klauser 
Reviewed-by: Brad Fitzpatrick

runtime: add support for VDSO on ppc64x for use in walltime/nanotime

2018-08-31T13:12:31+00:00

This change adds support for VDSO on ppc64x, making it possible to
avoid a syscall in walltime and nanotime.

BenchmarkClockVDSOAndFallbackPaths/vDSO-192             20000000    66.0 ns/op
BenchmarkClockVDSOAndFallbackPaths/Fallback-192          1000000    1456 ns/op

Change-Id: I3373bd804b6f122961de3ae9d034e6ccf35748e6
Reviewed-on: https://go-review.googlesource.com/131135
Run-TryBot: Lynn Boger 
TryBot-Result: Gobot Gobot 
Reviewed-by: Lynn Boger

all: update comment URLs from HTTP to HTTPS, where possible

2018-06-01T21:52:00+00:00

Each URL was manually verified to ensure it did not serve up incorrect
content.

Change-Id: I4dc846227af95a73ee9a3074d0c379ff0fa955df
Reviewed-on: https://go-review.googlesource.com/115798
Reviewed-by: Ian Lance Taylor 
Run-TryBot: Ian Lance Taylor

runtime: use vDSO for clock_gettime on linux/arm64

2018-03-27T13:21:27+00:00

Use the __vdso_clock_gettime fast path via the vDSO on linux/arm64 to
speed up nanotime and walltime. This results in the following
performance improvement for time.Now on Cavium ThunderX:

name     old time/op  new time/op  delta
TimeNow   442ns ± 0%   163ns ± 0%  -63.16%  (p=0.000 n=10+10)

And benchmarks on VDSO

BenchmarkClockVDSOAndFallbackPaths/vDSO         10000000 166 ns/op
BenchmarkClockVDSOAndFallbackPaths/Fallback     3000000 456 ns/op

Change-Id: I326118c6dff865eaa0569fc45d1fc1ff95cb74f6
Reviewed-on: https://go-review.googlesource.com/99855
Run-TryBot: Tobias Klauser 
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor

runtime: get traceback from VDSO code

2018-03-07T23:35:25+00:00

Currently if a profiling signal arrives while executing within a VDSO
the profiler will report _ExternalCode, which is needlessly confusing
for a pure Go program. Change the VDSO calling code to record the
caller's PC/SP, so that we can do a traceback from that point. If that
fails for some reason, report _VDSO rather than _ExternalCode, which
should at least point in the right direction.

This adds some instructions to the code that calls the VDSO, but the
slowdown is reasonably negligible:

name                                  old time/op  new time/op  delta
ClockVDSOAndFallbackPaths/vDSO-8      40.5ns ± 2%  41.3ns ± 1%  +1.85%  (p=0.002 n=10+10)
ClockVDSOAndFallbackPaths/Fallback-8  41.9ns ± 1%  43.5ns ± 1%  +3.84%  (p=0.000 n=9+9)
TimeNow-8                             41.5ns ± 3%  41.5ns ± 2%    ~     (p=0.723 n=10+10)

Fixes #24142

Change-Id: Iacd935db3c4c782150b3809aaa675a71799b1c9c
Reviewed-on: https://go-review.googlesource.com/97315
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Austin Clements

runtime: rename vdso symbols to use camel case

2018-03-05T19:12:32+00:00

This was originally C code using names with underscores, which were
retained when the code was rewritten into Go. Change the code to use
Go-like camel case names.

The names that come from the ELF ABI are left unchanged.

Change-Id: I181bc5dd81284c07bc67b7df4635f4734b41d646
Reviewed-on: https://go-review.googlesource.com/98520
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Tobias Klauser 
Reviewed-by: Brad Fitzpatrick

runtime: use vDSO for clock_gettime on linux/arm

2018-03-03T12:12:58+00:00

Use the __vdso_clock_gettime fast path via the vDSO on linux/arm to
speed up nanotime and walltime. This results in the following
performance improvement for time.Now on a RaspberryPi 3 (running
32bit Raspbian, i.e. GOOS=linux/GOARCH=arm):

name     old time/op  new time/op  delta
TimeNow  0.99µs ± 0%  0.39µs ± 1%  -60.74%  (p=0.000 n=12+20)

Change-Id: I3598278a6c88d7f6a6ce66c56b9d25f9dd2f4c9a
Reviewed-on: https://go-review.googlesource.com/98095
Reviewed-by: Ian Lance Taylor 
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot

runtime: update URL of the Linux vDSO parser tool

2018-01-16T15:11:05+00:00

The tool was moved to tools/Testing/selftests within the Linux kernel
source tree. Adjust the URL in the comments of vdso_linux.go

Change-Id: I86b9cae4b898c4a45bc7c54891ce6ead91a22670
Reviewed-on: https://go-review.googlesource.com/87815
Reviewed-by: Ian Lance Taylor

runtime: use vDSO on linux/386 to improve time.Now performance

2017-10-13T14:41:04+00:00

This change adds support for accelerating time.Now by using
the __vdso_clock_gettime fast-path via the vDSO on linux/386
if it is available.

When the vDSO path to the clocks is available, it is typically
5x-10x faster than the syscall path (see benchmark extract
below).  Two such calls are made for each time.Now() call
on most platforms as of go 1.9.

- Add vdso_linux_386.go, containing the ELF32 definitions
  for use by vdso_linux.go, the maximum array size, and
  the symbols to be located in the vDSO.

- Modify runtime.walltime and runtime.nanotime to check for
  and use the vDSO fast-path if available, or fall back to
  the existing syscall path.

- Reduce the stack reservations for runtime.walltime and
  runtime.monotime from 32 to 16 bytes. It appears the syscall
  path actually only needed 8 bytes, but 16 is now needed to
  cover the syscall and vDSO paths.

- Remove clearing DX from the syscall paths as clock_gettime
  only takes 2 args (BX, CX in syscall calling convention),
  so there should be no need to clear DX.

The included BenchmarkTimeNow was run with -cpu=1 -count=20
on an "Intel(R) Celeron(R) CPU J1900 @ 1.99GHz", comparing
released go 1.9.1 vs this change. This shows a gain in
performance on linux/386 (6.89x), and that no regression
occurred on linux/amd64 due to this change.

Kernel: linux/i686, GOOS=linux GOARCH=386
   name      old time/op  new time/op  delta
   TimeNow   978ns ± 0%   142ns ± 0%  -85.48%  (p=0.000 n=16+20)

Kernel: linux/x86_64, GOOS=linux GOARCH=amd64
   name      old time/op  new time/op  delta
   TimeNow   125ns ± 0%   125ns ± 0%   ~       (all equal)

Gains are more dramatic in virtualized environments,
presumably due to the overhead of virtualizing the syscall.

Fixes #22190

Change-Id: I2f83ce60cb1b8b310c9ced0706bb463c1b3aedf8
Reviewed-on: https://go-review.googlesource.com/69390
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor

runtime: factor amd64 specifics from vdso_linux.go

2017-10-13T02:04:20+00:00

This is a preparation step for adding vDSO support on linux/386.

This change relocates the elf64 and amd64 specifics from
vdso_linux.go to a new vdso_linux_amd64.go.

This should enable vdso_linux.go to be used for vDSO
support on linux architectures other than amd64.

- Relocate the elf64X structure definitions appropriate to amd64,
  and change their names to elfX so that the code in vdso_linux.go
  is ELFnn-agnostic.

- Relocate the sym_keys and corresponding __vdso_* variables
  appropriate to amd64.

- Provide an amd64-specific constant for the maximum byte size of
  an array, and use this in vdso_linux.go to compute constants for
  sizing the elf structure arrays traversed in the loaded vDSO.

Change-Id: I1edb4e4ec9f2d79b7533aa95fbd09f771fa4edef
Reviewed-on: https://go-review.googlesource.com/69391
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor